1. Field of the Invention
The present invention relates to an apparatus and a method for controlling a motor capable of selectively performing a proportional control and a proportional integral control according to an average error value and adjusting a gain value of the selected control.
2. Description of the Related Art
Proportional integral differential (PID) controllers, feedback controls allowing an output of a system to maintain a level equal to that of a reference voltage, based on deviation between a control variable and a reference input, are the most commonly used controllers in industrial facilities at present.
Specifically, PID controllers have a structure in which an output of an object to be controlled is measured and compared to a desired reference value or a set point, to thereby calculate an error therebetween, and then calculating a control value required for controlling the object by using the error value.
In the PID controller, proportional control is proportional to an error, a difference between the output of the object to be controlled and a target value, and an integral control is obtained by integrating the error for time, is used to remove a normal state error, and may generate a large overshoot in the case in which a gain thereof is relatively large. In addition, a differential control is used to differentiate the error and predict a response to the error in order to decrease the overshoot.
A driving force of the proportional integral differential control is a magnitude of the error value. That is, process inputs are continuously fed back so that the output value arrives at the set point. In the same control variables, as the error value is increased, a higher control output is generated, and as a gap between the error values is narrowed, a small control output is generated.
In the proportional integral differential controller, suitable controlling variables should be set according to characteristics of the process, such that vibrations in a normal state are relatively low, and a speed of removing a generated disturbance is also increased. Deriving relatively optimal variables from a specific process, as described above, is referred to as “proportional integral differential tuning.”
However, a process model suggesting proportional integral differential tuning capable of implementing good control performance has not been suggested to date.
The following Related Art Document, related to an assisted power steering apparatus, discloses content in which the integral control is the main factor in performing the proportional integral control and gain value of the proportional control is changed according to speed, but does not disclose content in which the proportional control and the proportional integral control according to the average error value are selectively performed, and the error value is changed according to the average error value and the overshooting.